Duplicating equipment for lithographic reproduction requires a series of cylinders for handling the various elements involved in the lithographic duplicating process. It is conventional for lithographic duplication to use a master which is mounted on a master cylinder. An oleophilic ink and moisture are applied to the master while it is clamped on the master cylinder, to put it into condition for printing. Any areas of the master cylinder which are not covered by the master are exposed with the master to the application of ink and moisture. These exposed areas must not attract or hold ink. If any exposed areas of the cylinder accept ink from the ink form roller, this ink will then transfer to the blanket which is retained on the blanket cylinder and thence to any impression paper which contacts the blanket. Only the image portions on the master must retain ink; every other portion of the master, as well as the exposed areas of the master cylinder, must be free of ink.
Heretofore, these lithographic duplicating cylinders were commonly prepared by casting high-strength iron, such as Mehanite; thereafter the cylinder was ground and given a hard chromium surface using conventional electro-plating techniques. The electro-plated chromium surface was then treated to secure and retain its water receptivity by preventing the formation of any oxides on the surface. Aqueous acidified ammonium chloride plus excess chalk was commonly used for this treatment.
The electro-plating technique tends to highlight any irregularities such as pits, holes, or cracks in the cast surface. Accordingly, the cast iron cylinders that would be acceptable for chrome plating required highly uniform surfaces; rejects were numerous.